Control apparatus for internal combustion engine

ABSTRACT

An engine ECU executes a program including the steps of calculating an in-cylinder injector&#39;s injection ratio; if the ratio is 1, calculating an amount of cold state spark advance by employing a function f( 1 ) having the engine&#39;s temperature as a parameter; if the ratio is 0, calculating an amount of cold state spark advance by employing a function f( 2 ) having the engine&#39;s temperature as a parameter; and if the ratio is larger than 0 and smaller than 1, calculating an amount of cold state spark advance by employing a function f( 3 ) having the engine&#39;s temperature and the ratio as parameters.

This nonprovisional application is based on Japanese Patent ApplicationsNos. 2004-328143 and 2005-078461 filed with the Japan Patent Office onNov. 11, 2004 and Mar. 18, 2005, respectively, the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control apparatus for an internalcombustion engine having a first fuel injection mechanism (anin-cylinder injector) for injecting a fuel into a cylinder and a secondfuel injection mechanism (an intake manifold injector) for injecting afuel into an intake manifold or an intake port, and relates particularlyto a technique for determining a timing of ignition with a fuelinjection ratio between the first and second fuel injection mechanismsconsidered.

2. Description of the Background Art

An internal combustion engine having an intake manifold injector forinjecting a fuel into an intake manifold of the engine and anin-cylinder injector for always injecting a fuel into a combustionchamber of the engine, and configured to stop fuel injection from theintake manifold injector when the engine load is lower than a presetload and to cause fuel injection from the intake manifold injector whenthe engine load is higher than the set load, is known.

In such an internal combustion engine, one configured to switch betweenstratified charge combustion and homogeneous combustion in accordancewith its operation state is known. In the stratified charge combustion,the fuel is injected from the in-cylinder injector during a compressionstroke to form a stratified air-fuel mixture locally around a sparkplug, for lean combustion of the fuel. In the homogeneous combustion,the fuel is diffused in the combustion chamber to form a homogeneousair-fuel mixture, for combustion of the fuel.

Japanese Patent Laying-Open No. 2001-020837 discloses a fuel injectioncontrol apparatus for an engine that switches between stratified chargecombustion and homogeneous combustion in accordance with an operationstate and that has a main fuel injection valve for injecting a fueldirectly into a combustion chamber and a secondary fuel injection valvefor injecting a fuel into an intake port of each cylinder. This fuelinjection control apparatus for the engine is characterized in that thefuel injection ratio between the main fuel injection valve and thesecondary fuel injection valve is set in a variable manner based on anoperation state of the engine.

According to this fuel injection control apparatus for the engine, thestratified charge combustion is carried out using only the main fuelinjection valve directly injecting the fuel into the combustion chamber,while the homogeneous combustion is carried out using both the main fuelinjection valve and the secondary fuel injection valve (or using onlythe secondary fuel injection valve in some cases). This can keep thecapacity of the main fuel injection valve small, even in the case of anengine of high power. Linearity in injection duration/injection quantitycharacteristic of the main fuel injection valve in a low-load regionsuch as during idling is improved, which in turn improves accuracy incontrol of the fuel injection quantity. Accordingly, it is possible tomaintain favorable stratified charge combustion, and thus to improvestability of the low-load operation such as idling. In the homogeneouscombustion, both the main and secondary fuel injection valves areemployed, so that the benefit of the direct fuel injection and thebenefit of the intake port injection are both enjoyed. Accordingly,favorable homogeneous combustion can also be maintained.

In the fuel injection control apparatus for the engine disclosed inJapanese Patent Laying-Open No. 2001-020837, the stratified chargecombustion and the homogeneous combustion are employed according-to thesituations, which complicates ignition control, injection control andthrottle control, and requires control programs corresponding to therespective combustion manners. Particularly, upon switching between thecombustion manners, these controls require considerable changes, makingit difficult to realize desirable controls (of fuel efficiency, emissionpurification performance) at the time of transition. Further, in thestratified combustion region where lean combustion is carried out, thethree-way catalyst does not work, in which case a lean NOx catalystneeds to be used, leading to an increased cost.

Based on the foregoing, an engine has also been developed which does notprovide stratified charge combustion, and thus does not need control forswitching between the stratified charge combustion and the homogeneouscombustion and does not require an expensive lean NOx catalyst.

In controlling the engine to be ignited with its coolant having lowertemperature, spark advance is introduced for correction. This is becausewhen the coolant has lower temperature (poorer atomization is provided)lower combustion rates are provided and the engine is less prone toknock. The spark advance can provide an increased period of time betweenignition and exhaust, and despite lower combustion rates the air fuelmixture can sufficiently be combusted.

In a cold state, however, for a range shared by an intake manifoldinjector injecting fuel into an intake manifold (or port) having lowtemperature in a cold state and an in-cylinder injector injecting thefuel into a cylinder having high temperature despite the cold state toboth inject the fuel the fuel is atomized differently. As such, the fuelinjected through the in-cylinder injector and that through the intakemanifold injector have different conditions, respectively. The fuelatomized differently forms air fuel mixtures having different conditionsand hence combusting differently, and the air fuel mixtures combustingdifferently require different optimal timings of ignition. As such,using the coolant's temperature alone to calculate an amount of sparkadvance cannot provide an accurate timing of ignition (or an accurateamount of spark advance). Furthermore, not only in the cold state but atransitional period from the cold state to a warm state as well, for arange shared by the intake manifold and in-cylinder injectors to bothinject the fuel the temperature in the cylinder and that at the intakeport increase at different rates. As such, using the coolant'stemperature alone to calculate an amount of spark advance cannot providean accurate amount of spark advance. Note that Japanese PatentLaying-open No. 2001-20837 only discloses that each injector is drivento achieve a fuel injection ratio corresponding to the operation stateof interest and a timing of ignition is set, and the document does notprovide a solution to the problem described above.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a control apparatus foran internal combustion engine having first and second fuel injectionmechanisms bearing shares, respectively, of injecting fuel into acylinder and an intake manifold, respectively, that can calculate anaccurate amount of variation introduced to time ignition in a cold stateand a transitional period from the cold state to a warm state when thefuel injection mechanisms share injecting the fuel.

The present invention in one aspect provides a control apparatus for aninternal combustion engine that controls an internal combustion enginehaving a first fuel injection mechanism injecting fuel into a cylinderand a second fuel injection mechanism injecting the fuel into an intakemanifold. The control apparatus includes: a controller controlling thefirst and second fuel injection mechanisms to bear shares, respectively,of injecting the fuel at a ratio calculated as based on a conditionrequired for the internal combustion engine; a detector detecting atemperature of the internal combustion engine; and an ignition timingcontroller controlling an ignition device to vary a timing of ignition.The ignition timing controller uses the ratio and the temperature tocalculate an amount of variation introduced to time the internalcombustion engine to be ignited in a cold state and applies the amountto control the ignition device to vary the timing of ignition.

In the present invention, for a range shared by the first fuel injectionmechanism (e.g., an in-cylinder injector) and the second fuel injectionmechanism (e.g., an intake manifold injector) to both inject the fuelthe cylinder's interior and the intake port increase in temperature atdifferent rates. In a cold state and a transitional period from the coldstate to a warm state, because of this difference in temperature, sparkadvance or retard is introduced at different degrees. The ignitiontiming controller considers a ratio between the fuel injected into thecylinder and that injected into the intake port and calculates as basedon the internal combustion engine's temperature (e.g., that of a coolantof an engine) an amount of spark advance or retard (collectivelyreferred to as an amount of variation introduced to time ignition) inthe cold state. Thus the internal combustion engine having two fuelinjection mechanisms that share injecting fuel into different portionscan have an accurate spark advance or retard in the cold state. Thus acontrol apparatus for an internal combustion engine can be provided thatcan calculate an accurate amount of variation introduced to timeignition in a cold state and a transitional period from the cold stateto a warm state when fuel injection mechanisms share injecting the fuel.

The present invention in another aspect provides a control apparatus foran internal combustion engine that controls an internal combustionengine having a first fuel injection mechanism injecting fuel into acylinder and a second fuel injection mechanism injecting the fuel intoan intake manifold. The control apparatus includes: a controllercontrolling the first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for the internal combustion engine; adetector detecting a temperature of the internal combustion engine; acalculator calculating a reference timing of ignition; and an ignitiontiming controller using an amount of variation introduced to timeignition to control an ignition device to vary the reference timing ofignition. The ignition timing controller uses the ratio and thetemperature to calculate an amount of variation introduced to time theinternal combustion engine to be ignited in a cold state and applies theamount to control the ignition device to vary the reference timing ofignition.

In the present invention for a range shared by the first fuel injectionmechanism (e.g., an in-cylinder injector) and the second fuel injectionmechanism (e.g., an intake manifold injector) to both inject the fuelthe cylinder's interior and the intake port increase in temperature atdifferent rates. In a cold state and a transitional period from the coldstate to a warm state, because of this difference in temperature, sparkadvance or retard is introduced at different degrees. The ignitiontiming controller considers a ratio between the fuel injected into thecylinder and that injected into the intake port and calculates as basedon the internal combustion engine's temperature (e.g., that of a coolantof an engine) an amount of spark advance or retard for correction in thecold state. This amount is used to vary a reference timing of ignitioncalculated as based on the internal combustion engine's operation state.Thus the internal combustion engine having two fuel injection mechanismsthat share injecting fuel into different portions can achieve anaccurately varied timing of ignition in the cold state. Thus a controlapparatus for an internal combustion engine can be provided that cancalculate an accurate amount of variation introduced to time ignition ina cold state and a transitional period from the cold state to a warmstate when fuel injection mechanisms share injecting the fuel.

The present invention in still another aspect provides a controlapparatus for an internal combustion engine that controls an internalcombustion engine having a first fuel injection mechanism injecting fuelinto a cylinder and a second fuel injection mechanism injecting the fuelinto an intake manifold. The control apparatus includes: a controllercontrolling the first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for the internal combustion engine; adetector detecting a temperature of the internal combustion engine; andan ignition timing controller controlling an ignition device to vary atiming of ignition. The ignition timing controller uses the ratio andthe temperature to calculate an amount of spark advance of the internalcombustion engine in a cold state and applies the amount to control theignition device to vary the timing of ignition.

In the present invention, for a range shared by the first fuel injectionmechanism (e.g., an in-cylinder injector) and the second fuel injectionmechanism (e.g., an intake manifold injector) to both inject the fuelthe cylinder's interior and the intake port increase in temperature atdifferent rates. In a cold state and a transitional period from the coldstate to a warm state, because of this difference in temperature, sparkadvance is introduced at different degrees. The ignition timingcontroller considers a ratio between the fuel injected into the cylinderand that injected into the intake port and calculates as based on theinternal combustion engine's temperature (e.g., that of a coolant of anengine) an amount of spark advance in the cold state. Thus the internalcombustion engine having two fuel injection mechanisms that shareinjecting fuel into different portions can have an accurate sparkadvance in the cold state. Thus a control apparatus for an internalcombustion engine can be provided that can calculate an accurate amountof spark advance in a cold state and a transitional period from the coldstate to a warm state when fuel injection mechanisms share injecting thefuel.

The present invention in still another aspect provides a controlapparatus for an internal combustion engine that controls an internalcombustion engine having a first fuel injection mechanism injecting fuelinto a cylinder and a second fuel injection mechanism injecting the fuelinto an intake manifold. The control apparatus includes: a controllercontrolling the first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for the internal combustion engine; adetector detecting a temperature of the internal combustion engine; acalculator calculating a reference timing of ignition; and an ignitiontiming controller using an amount of spark advance for correction tocontrol an ignition device to vary the reference timing of ignition. Theignition timing controller uses the ratio and the temperature tocalculate an amount of spark advance of the internal combustion enginefor correction in a cold state and applies the amount to control theignition device to vary the reference timing of ignition.

In the present invention, for a range shared by the first fuel injectionmechanism (e.g., an in-cylinder injector) and the second fuel injectionmechanism (e.g., an intake manifold injector) to both inject the fuelthe cylinder's interior and the intake port increase in temperature atdifferent rates. In a cold state and a transitional period from the coldstate to a warm state, because of this difference in temperature, sparkadvance is introduced at different degrees. The ignition timingcontroller considers a ratio between the fuel injected into the cylinderand that injected into the intake port and calculates as based on theinternal combustion engine's temperature (e.g., that of a coolant of anengine) an amount of spark advance for correction in the cold state.This amount is used to vary a reference timing of ignition calculated asbased on the internal combustion engine's operation state. Thus theinternal combustion engine having two fuel injection mechanisms thatshare injecting fuel into different portions can have an accurate sparkadvance in the cold state. Thus a control apparatus for an internalcombustion engine can be provided that can calculate an accurate amountof spark advance in a cold state and a transitional period from the coldstate to a warm state when fuel injection mechanisms share injecting thefuel.

Preferably the ignition timing controller calculates the amount of sparkadvance to be decreased when the first fuel injection mechanism isincreased in the ratio.

In accordance with the present invention, as the first fuel injectionmechanism an in-cylinder injector injecting fuel into a cylinder exists,and the cylinder's internal temperature is higher than the intake port'stemperature. As such, if the in-cylinder injector injects the fuel athigher ratios, it is not necessary to introduce a significant sparkadvance. Despite small spark advance, combustion as desired can beachieved.

Still preferably the ignition timing controller calculates the amount ofspark advance to be increased when the second fuel injection mechanismis increased in the ratio.

In accordance with the present invention, as the second fuel injectionmechanism an intake manifold injector injecting fuel into an intakemanifold exists, and the intake port's temperature is lower than thecylinder's internal temperature. As such, if the intake manifoldinjector injects the fuel at higher ratios, significant spark advancecan be introduced to achieve combustion as desired.

Still preferably the ignition timing controller calculates the amount ofspark advance to be decreased when the temperature is increased.

In accordance with the present invention higher temperatures in theinternal combustion engine help the fuel to atomize. As such, a largespark advance is not required and despite a small spark advancecombustion as desired can be achieved.

Still preferably the ignition timing controller calculates the amount ofspark advance to be increased when the temperature is decreased.

In accordance with the present invention lower temperatures in theinternal combustion engine prevent the fuel from atomizing. Accordingly,a large spark advance is introduced so that combustion as desired can beachieved.

The present invention in still another aspect provides a controlapparatus for an internal combustion engine that controls an internalcombustion engine having a first fuel injection mechanism injecting fuelinto a cylinder and a second fuel injection mechanism injecting the fuelinto an intake manifold. The control apparatus includes: a controllercontrolling the first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for the internal combustion engine, theratio including preventing one of the fuel injection mechanisms frominjecting the fuel; a detector detecting a temperature of the internalcombustion engine; a storage storing a reference timing of ignition andan amount of variation introduced to time ignition in a cold state; andan ignition timing controller controlling an ignition device by varyingthe reference timing of ignition by the amount to provide a variedtiming of ignition. The storage stores the amount of variationintroduced to time the internal combustion engine to be ignited in thecold state, the amount being calculated as based on a condition of amixture of the fuel injected through the fuel injection mechanism andair.

In accordance with the present invention, in a cold state, for a rangeshared by the first fuel injection mechanism (e.g., an in-cylinderinjector) and the second fuel injection mechanism (e.g., an intakemanifold injector) to both inject the fuel the cylinder receiving thefuel injected through the first fuel injection mechanism and the intakemanifold receiving the fuel injected through the second fuel injectionmechanism are high and low, respectively, in temperature, whichcontributes to a difference between how the fuel is atomized in thecylinder (satisfactorily) and how it is atomized in the intake manifold(unsatisfactorily) and hence a difference between a mixture of the fuelin the cylinder and air and that of the fuel in the intake manifold andair. More specifically the difference is for one reason caused by howdifferently the fuel is atomized in a cold state. The in-cylinderinjector injects the fuel into the hot cylinder even in the cold state.As such, the fuel can be atomized satisfactorily and thus mixed with airto form a satisfactorily homogeneous air fuel mixture allowing a highcombustion rate. In contrast, the intake manifold injector injects thefuel into the cold intake manifold in the cold state. As such, the fuelis atomized insufficiently and thus mixed with air to form aninhomogeneous air fuel mixture resulting in a low combustion rate.Accordingly the ignition device is controlled to achieve an optimaltiming of ignition by varying a reference timing of ignition by anamount of variation introduced to time ignition that is calculated asbased on an air fuel mixture's condition (such as how it is atomized,how homogeneous it is, and the like) that reflects the fuel injectionmechanisms' fuel injection ratio and in addition thereto the internalcombustion engine's temperature and the like. Thus the internalcombustion engine having two fuel injection mechanisms that shareinjecting fuel and provide air fuel mixtures having different conditionscan achieve an accurately set timing of ignition. As a result a controlapparatus that can calculate an accurate timing of ignition can beprovided for an internal combustion engine having first and second fuelinjection mechanisms bearing shares, respectively, of injecting fuel toinject the fuel into a cylinder and an intake manifold, respectively,that are implemented by two types of fuel injection mechanisms injectingfuel differently.

Preferably the storage stores the amount calculated from the temperatureand the ratio.

In accordance with the present invention the temperature and the ratiocontribute to how the fuel is atomized, which in turn contributes to howan air fuel mixture is formed, and therefrom an amount of variationintroduced to time ignition is calculated. The ignition device iscontrolled by varying a reference timing of ignition by the calculatedamount to obtain an optimal timing of ignition.

Still preferably the storage stores the amount in a map.

In accordance with the present invention an optimal timing of ignitionobtained by advancing or retarding a reference timing of ignition by avariation introduced to time ignition can be determined from an amountof variation introduced to time ignition that is stored in a map asbased on a fuel injection ratio of the in-cylinder and intake manifoldinjectors.

Still preferably, the storage stores the amount divided into a first mapapplied when the first fuel injection mechanism alone injects the fuel,a second map applied when the second fuel injection mechanism aloneinjects the fuel, and a third map applied when the first and second fuelinjection mechanisms inject the fuel.

In accordance with the present invention the fuel injection ratio andthe internal combustion engine's temperature contribute to how an airfuel mixture is formed (e.g., how it is atomized, how homogeneous it is,and the like). When an in-cylinder injector corresponding to one exampleof the first fuel injection mechanism and an intake manifold injectorcorresponding to one example of the second fuel injection mechanism bearshares, respectively, of injecting fuel, an amount of variation from areference timing of ignition is stored in a map divided into a first mapapplied when the in-cylinder injector alone injects the fuel, a secondmap applied when the intake manifold injector alone injects the fuel,and a third map applied when the in-cylinder and intake manifoldinjectors inject the fuel. A map can be selected as based on a fuelinjection ratio between the in-cylinder and intake manifold injectors todetermine an amount of variation from the reference timing of ignition.Each map can store the amount of variation introduced to time ignitionwith the internal combustion engine's temperature serving as aparameter.

Still more preferably the first map provides the amount set to providespark retard.

In accordance with the present invention in the first map applied whenthe first fuel injection mechanism (e.g., an in-cylinder injector) aloneinjects fuel the fuel injected through the in-cylinder injector (atcompression stroke in particular) is atomized satisfactorily despite acold state and thus mixed with air to form a satisfactorily homogeneousair fuel mixture allowing a high combustion rate. Accordingly,basically, the map stores an amount of variation introduced to timeignition that sets a timing of ignition to be retarded. In particular,such tendency is increased as the internal combustion engine has highertemperature. Accordingly the internal combustion engine's temperaturecan be set as a parameter. It should be noted however that while thefuel injected through the in-cylinder injector is injected into the hotcylinder and thus satisfactorily atomized, it is mixed with air beforeignition for a short period of time. As such, while the fuel issatisfactorily atomized, the fuel mixed with air may not providesatisfactory homogeneity with the air. Accordingly an amount ofvariation introduced to time ignition is determined from a relationshipbetween an air fuel mixture's insufficient homogeneity resulting from ashort period of time for mixture that is attributed to the in-cylinderinjector and the fuel's sufficient atomization attributed to thecylinder's high internal temperature.

Still preferably the first map provides the amount set to provide sparkadvance.

In accordance with the present invention in the second map applied whenthe second fuel injection mechanism (e.g., an intake manifold injector)alone injects fuel the fuel injected through the intake manifoldinjector is atomized unsatisfactorily in a cold state and thus mixedwith air to form an inhomogeneous air fuel mixture contributing to a lowcombustion rate. Accordingly, basically, the map stores an amount ofvariation introduced to time ignition that sets a timing of ignition tobe advanced. It should be noted however that despite the cold state thefuel injected through the intake manifold injector is mixed with airbefore ignition for a long period of time. As such, despite itsinsufficient atomization, the fuel mixed with air may providesatisfactory homogeneity with the air. Accordingly an amount ofvariation introduced to time ignition is determined from a relationshipbetween an air fuel mixture's sufficient homogeneity resulting from along period of time for mixture that is attributed to the intakemanifold injector and the fuel's insufficient atomization attributed tothe intake manifold's low internal temperature.

Still preferably the third map provides the amount set to provide sparkretard when the first fuel injection mechanism is increased in theratio.

When the first fuel injection mechanism (e.g., an in-cylinder injector)injecting fuel into a hot cylinder despite a cold state and thusallowing the fuel to be satisfactorily atomized and thus mixed with airto form a mixture allowing a high combustion rate has a higher fuelinjection ratio, a more sufficient period of time for combustion can beensured despite an amount of variation set to provide spark retard thanwhen the second fuel injection mechanism (e.g., an intake manifoldinjector) injecting the fuel into a cold intake manifold in the coldstate and thus preventing the fuel from being satisfactorily atomizedand mixed with air to form a mixture allowing a high combustion rate hasa higher fuel injection ratio. Thus the internal combustion enginehaving two fuel injection mechanisms that bear shares, respectively, ofinjecting fuel and provide air fuel mixtures having differentconditions, respectively, can achieve an accurately set timing ofignition that can prevent detrimental effects attributed to excessivespark retard and advance.

Still preferably the third map provides the amount set to provide sparkadvance when the second fuel injection mechanism is increased in theratio.

When the second fuel injection mechanism (e.g., an intake manifoldinjector) injecting fuel into a cold intake manifold in a cold state andthus preventing the fuel from being satisfactorily atomized and mixedwith air to form a mixture contributing to a high combustion rate has ahigher fuel injection ratio, an amount of variation introduced to timeignition can be provided for spark advance to ensure a more sufficientperiod of time for combustion (from a timing of ignition to that ofstarting an exhaust stroke) than when the first fuel injection mechanism(e.g., an in-cylinder injector) injecting the fuel into a hot cylinderdespite the cold state and thus allowing the fuel to be satisfactorilyatomized and thus mixed with air to form a mixture allowing a highcombustion rate has a higher fuel injection ratio. Thus the internalcombustion engine having two fuel injection mechanisms that bear shares,respectively, of injecting fuel and provide air fuel mixtures havingdifferent conditions, respectively, can achieve an accurately set timingof ignition that can prevent detrimental effects attributed to excessivespark retard and advance.

Still preferably the first fuel injection mechanism is an in-cylinderinjector and the second fuel injection mechanism is an intake manifoldinjector.

In accordance with the present invention a control apparatus can beprovided that calculate an accurate amount of spark advance for aninternal combustion engine having separately provided first and secondfuel injection mechanisms implemented by an in-cylinder injector and anintake manifold injector to share injecting fuel when they shareinjecting the fuel in a cold state and a transitional period from thecold state to a warm state.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic configuration diagram of an engine system controlledby a control apparatus according to an embodiment of the presentinvention.

FIG. 2 is a flowchart of a program executed by an engine ECU.

FIG. 3 shows an example of a map of shared injection.

FIG. 4 illustrates how the engine's operation state varies.

FIGS. 5 and 7 show a DI ratio map for a warm state of an engine to whichthe present control apparatus is suitably applied.

FIGS. 6 and 8 show a DI ratio map for a cold state of an engine to whichthe present control apparatus is suitably applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter reference will be made to the drawings to describe thepresent invention in an embodiment. In the following descriptionidentical components are identically denoted. They are also identical inname and function. Note that while the following description is providedexclusively in conjunction with spark advance in a cold state, thepresent invention is not limited to such advance. The present inventionalso includes once introducing a spark advance and then a spark retardand introducing a spark retard from a reference timing of ignition.Furthermore, a relationship between a smaller spark advance for a higherratio of fuel injected through an in-cylinder injector and asignificantly large spark advance for a higher ratio of fuel injectedthrough an intake manifold injector, can be inverted. For example if theperformance of an in-cylinder injector 100 as a discrete injector andthat of an intake manifold injector 120 as a discrete injectorcontribute to less sufficient atomization of the fuel injected throughin-cylinder injector 100 than that of the fuel injected through intakemanifold injector 120 for the same engine coolant temperature THW, thefuel injection ratio-spark advance relationship described above can beinverted.

FIG. 1 is a schematic configuration diagram of an engine system that iscontrolled by an engine ECU (Electronic Control Unit) implementing thecontrol apparatus for an internal combustion engine according to anembodiment of the present invention. In FIG. 1, an in-line 4-cylindergasoline engine is shown, although the application of the presentinvention is not restricted to such an engine.

As shown in FIG. 1, the engine 10 includes four cylinders 112, eachconnected via a corresponding intake manifold 20 to a common surge tank30. Surge tank 30 is connected via an intake duct 40 to an air cleaner50. An airflow meter 42 is arranged in intake duct 40, and a throttlevalve 70 driven by an electric motor 60 is also arranged in intake duct40. Throttle valve 70 has its degree of opening controlled based on anoutput signal of an engine ECU 300, independently from an acceleratorpedal 100. Each cylinder 112 is connected to a common exhaust manifold80, which is connected to a three-way catalytic converter 90.

Each cylinder 112 is provided with an in-cylinder injector 110 forinjecting fuel into the cylinder and an intake manifold injector 120 forinjecting fuel into an intake port or/and an intake manifold. Injectors110 and 120 are controlled based on output signals from engine ECU 300.Further, in-cylinder injector 110 of each cylinder is connected to acommon fuel delivery pipe 130. Fuel delivery pipe 130 is connected to ahigh-pressure fuel pump 150 of an engine-driven type, via a check valve140 that allows a flow in the direction toward fuel delivery pipe 130.In the present embodiment, an internal combustion engine having twoinjectors separately provided is explained, although the presentinvention is not restricted to such an internal combustion engine. Forexample, the internal combustion engine may have one injector that caneffect both in-cylinder injection and intake manifold injection.

As shown in FIG. 1, the discharge side of high-pressure fuel pump 150 isconnected via an electromagnetic spill valve 152 to the intake side ofhigh-pressure fuel pump 150. As the degree of opening of electromagneticspill valve 152 is smaller, the quantity of the fuel supplied fromhigh-pressure fuel pump 150 into fuel delivery pipe 130 increases. Whenelectromagnetic spill valve 152 is fully open, the fuel supply fromhigh-pressure fuel pump 150 to fuel delivery pipe 130 is stopped.Electromagnetic spill valve 152 is controlled based on an output signalof engine ECU 300.

Each intake manifold injector 120 is connected to a common fuel deliverypipe 160 on a low pressure side. Fuel delivery pipe 160 andhigh-pressure fuel pump 150 are connected via a common fuel pressureregulator 170 to a low-pressure fuel pump 180 of an electricmotor-driven type. Further, low-pressure fuel pump 180 is connected viaa fuel filter 190 to a fuel tank 200. Fuel pressure regulator 170 isconfigured to return a part of the fuel discharged from low-pressurefuel pump 180 back to fuel tank 200 when the pressure of the fueldischarged from low-pressure fuel pump 180 is higher than a preset fuelpressure. This prevents both the pressure of the fuel supplied to intakemanifold injector 120 and the pressure of the fuel supplied tohigh-pressure fuel pump 150 from becoming higher than theabove-described preset fuel pressure.

Engine ECU 300 is implemented with a digital computer, and includes aROM (Read Only Memory) 320, a RAM (Random Access Memory) 330, a CPU(Central Processing Unit) 340, an input port 350, and an output port360, which are connected to each other via a bidirectional bus 310.

Airflow meter 42 generates an output voltage that is proportional to anintake air quantity, and the output voltage is input via an A/Dconverter 370 to input port 350. A coolant temperature sensor 380 isattached to engine 10, and generates an output voltage proportional to acoolant temperature of the engine, which is input via an AID converter390 to input port 350.

A fuel pressure sensor 400 is attached to fuel delivery pipe 130, andgenerates an output voltage proportional to a fuel pressure within fueldelivery pipe 130, which is input via an A/D converter 410 to input port350. An air-fuel ratio sensor 420 is attached to an exhaust manifold 80located upstream of three-way catalytic converter 90. Air-fuel ratiosensor 420 generates an output voltage proportional to an oxygenconcentration within the exhaust gas, which is input via an A/Dconverter 430 to input port 350.

Air-fuel ratio sensor 420 of the engine system of the present embodimentis a full-range air-fuel ratio sensor (linear air-fuel ratio sensor)that generates an output voltage proportional to the air-fuel ratio ofthe air-fuel mixture burned in engine 10. As air-fuel ratio sensor 420,an O₂ sensor may be employed, which detects, in an on/off manner,whether the air-fuel ratio of the air-fuel mixture burned in engine 10is rich or lean with respect to a theoretical air-fuel ratio.

Accelerator pedal 100 is connected with an accelerator pedal positionsensor 440 that generates an output voltage proportional to the degreeof press down of accelerator pedal 100, which is input via an A/Dconverter 450 to input port 350. Further, an engine speed sensor 460generating an output pulse representing the engine speed is connected toinput port 350. ROM 320 of engine ECU 300 prestores, in the form of amap, values of fuel injection quantity that are set in association withoperation states based on the engine load factor and the engine speedobtained by the above-described accelerator pedal position sensor 440and engine speed sensor 460, and correction values thereof set based onthe engine coolant temperature.

With reference to the flowchart of FIG. 2 engine ECU 300 of FIG. 1executes a program having a structure for control, as describedhereinafter.

In step (S) 100 engine ECU 300 employs a map as shown in FIG. 3 tocalculate an injection ratio of in-cylinder injector 110. Hereinafterthis ratio will be referred to as “DI ratio r,” wherein 0≦r≦1. The mapused to calculate the ratio will be described later.

In S100 engine ECU 300 determines whether DI ratio r is 1, 0, or largerthan 0 and smaller than 1. If DI ratio r is 1 (r=1.0 in S110) theprocess proceeds to S120. If DI ratio r is 0 (r=0 in S110) the processproceeds to S130. If DI ratio r is larger than 0 and smaller than 1(0<r<1 in S110) the process proceeds to S140.

In S120 engine ECU 300 calculates an amount of cold state spark advancecorresponding to that of spark advance for correction in a cold statewhen in-cylinder injector 110 alone injects fuel. This is done forexample by employing a function f(1) to calculate an amount of coldstate spark advance=f(1)(THW). Note that “THW” represents thetemperature of a coolant of engine 10 as detected by coolant temperaturesensor 380.

Note that when the fuel injected through in-cylinder injector 110 andthat injected through intake manifold injector 120 are mixed with airthey provide air fuel mixtures having significantly differentconditions. In particular, in a cold state when the fuel injectedthrough in-cylinder injector 110 into a hot cylinder and that injectedthrough intake manifold injector 120 into a cold intake manifold aremixed with air they provide air fuel mixtures having significantlydifferent conditions. The fuel injected through intake manifold injector120 is atomized insufficiently and hence mixed with air to provide anair fuel mixture having an unsatisfactory (or inhomogeneous) conditionresulting in a low combustion rate. In contrast, the fuel injectedthrough in-cylinder injector 110 is satisfactorily atomized and hencemixed with air to provide an air fuel mixture having a satisfactory (orhomogeneous) condition allowing a high combustion rate.

Function f(1)(THW) is a function applied for DI ratio r=0 (i.e., whenin-cylinder injector 110 alone injects fuel). It is set to allow anamount of cold state spark advance to be minimized (including providinga spark retard from a reference timing of ignition.), since the fuelinjected through in-cylinder injector 110 and air can form asatisfactorily homogenous air fuel mixture allowing an increasedcombustion rate, and if ignition is timed to be maximally retarded asufficient period of time for combustion can still be ensured.

Despite that, the period after in-cylinder injector 110 injects the fuelbefore ignition is short. As such, while the fuel is satisfactorilyatomized, there is a tendency that a sufficient period of time is notprovided to ensure homogeneity. Thus a short period of time elapsingafter in-cylinder injector 110 injects the fuel and before ignitionaffects an air fuel mixture to be unsatisfactorily homogeneous.Accordingly, setting function f(1)(THW) while considering such a periodof time elapsing after fuel is injected and before ignition, can also beconsidered.

In S130 engine ECU 300 calculates an amount of cold state spark advancecorresponding to that of spark advance for correction in the cold statewhen intake manifold injector 120 alone injects fuel. This is done forexample by employing a function f(2) to calculate an amount of coldstate spark advance=f(2)(THW).

Function f(2)(THW) is a function applied for DI ratio r=0 (i.e., whenintake manifold injector 120 alone injects fuel). It is set to allow anamount of cold state spark advance to be maximized, since the fuelinjected through intake manifold injector 120 and air form aninhomogeneous air fuel mixture contributing to a decreased combustionrate, and accordingly ignition is timed to be maximally advanced toensure a sufficient period of time for combustion.

Despite that, the period after intake manifold injector 120 injects thefuel and before ignition is long. As such, while the fuel isunsatisfactorily atomized, there is a tendency that a sufficient periodof time is provided to ensure homogeneity. As such, a long period oftime elapsing after intake manifold injector 120 injects the fuel andbefore ignition affects an air fuel mixture to be satisfactorilyhomogeneous. Accordingly, setting function f(2)(THW) while consideringsuch a period of time elapsing after fuel is injected and beforeignition, can also be considered.

In S140 engine ECU 300 calculates an amount of cold state spark advancecorresponding to that of spark advance for correction in a cold statewhen in-cylinder and intake manifold injectors 110 and 120 bear shares,respectively, of injecting fuel. This is done for example by employing afunction f(3) to calculate an amount of cold state sparkadvance=f(3)(THW, r). Note that “r” represents a DI ratio.

In S150 engine ECU 300 calculates a timing of ignition for example byemploying a function g to calculate a timing of ignition=g (an amount ofcold state spark advance).

Reference will now be made to FIG. 3 to describe an injection ratio(0≦DI ratio r≦1) of in-cylinder injector 110 with an engine speed NE anda load factor KL of engine 10 serving as parameters.

In a low engine speed and high load range the fuel injected throughin-cylinder injector 10 is insufficiently mixed with air, and in thecombustion chamber the air fuel mixture tends to be inhomogeneous andthus provide unstable combustion. Accordingly, for this range, DI ratior is reduced to increase an injection ratio (1-r) of intake manifoldinjector 120 to sufficiently mix the air fuel mixture before it isintroduced into the combustion chamber.

In a high engine speed and low load range the air fuel mixture injectedthrough in-cylinder injector 10 is readily homogenized. Accordingly, DIratio r is increased. The fuel injected through in-cylinder injector 10is vaporized within the combustion chamber involving latent heat ofvaporization (by absorbing heat from the combustion chamber).Accordingly at the compression side the air fuel mixture is decreased intemperature and improved antiknock performance is provided. Furthermore,as the combustion chamber is decreased in temperature, improved intakeefficiency can be achieved and high power output expected. Furthermore,in-cylinder injector 110 can have its end, exposed in the combustionchamber, cooled by the fuel and thus have its injection hole preventedfrom having deposit adhering thereto.

As based on the configuration and flowchart as described above, engine10 in the present embodiment operates as described hereinafter. Notethat in the following description “if the engine's coolant varies intemperature” and other similar expressions indicate a transitionalperiod from a cold state to a warm state.

No Variation in DI Ratio R and Variation Present in Temperature ofCoolant for Engine

When engine 10 starts, normally the coolant increases in temperature.More specifically, in FIG. 4, the coolant increases in temperature froma temperature TH(1) corresponding to a point A to a temperature TH(2)corresponding to a point B. The DI ratio is calculated (S100) and if DIratio r is not found to have varied (e.g., r=0.7) a decision is madethat it is larger than 0 and smaller than 1 (0<r<1 in S110) and functionf(3) is accordingly used to calculate an amount of cold state sparkadvance by f(3) (THW, r) (S140).

In FIG. 4, for point A, by f(3) (TH(1), r), wherein r=0.7, an amount ofcold state spark advance is calculated as a spark advance for correction(1). With the amount of cold state spark advance set at the sparkadvance for correction (1), engine 10 is operated, and temperature THWincreases from TH(1) to TH(2) to reach point B. For point B, by f(3)(TH(2), r), wherein r=0.7, an amount of cold state spark advance iscalculated as a spark advance for correction (2). In other words, anamount of spark advance for correction is reduced from the spark advancefor correction (1) to the spark advance for correction (2) by avariation in amount of spark advance for correction, which is providedby the spark advance for correction (1) minus the spark advance forcorrection (2).

Variation Present in DI Ratio R and No Variation in Temperature ofCoolant for Engine

While engine 10 is started, the coolant may not vary depending on thevehicle's surrounding (temperature in particular). If in such a case theengine 10 operation state varies and DI ratio r drops from 0.7, i.e., inFIG. 4, while temperature TH(1) corresponding to point A is held, apoint C allowing DI ratio r smaller than 0.7 is attained (or it may bevice versa). The DI ratio is calculated and if DI ratio r is found tohave varied (for example from 0.7 to 0.5) a decision is made that DIratio r is still larger than 0 and smaller than 1 (0<r<1 in S100), andfunction f(3) is employed to calculate an amount of cold state sparkadvance by f(3) (THW, r) (S140).

In FIG. 4, for point A, by f(3) (TH(1), r), wherein r=0.7, an amount ofcold state spark advance is calculated. In this condition engine 10 isoperated, and while temperature THW is held at TH(1), DI ratio rdecreases to reach point C. For point C, by f(3) (TH(1), r), whereinr=0.5, an amount of cold state spark advance is calculated. Morespecifically, a spark advance is introduced by a variation in amount ofspark advance for correction. This indicates that a larger spark advanceis introduced as the port's temperature is lower than the cylinder'sinternal temperature and the fuel injected through intake manifoldinjector 120 is hard to atomize.

Variation Present in DI ratio R and Variation Present in Temperature ofCoolant for Engine

When engine 10 is started the coolant's temperature and DI ratio r mayboth vary. In such a case, in FIG. 4 point A corresponding totemperature TH(1) and DI ratio r=0.7 transitions to a point Dcorresponding to temperature TH(2) higher than TH(1) and a DI ratio rsmaller than 0.7. The DI ratio is calculated and if DI ratio r is foundto have varied (for example from 0.7 to 0.5) a decision is still madethat DI ratio r is larger than 0 and smaller than 1 (0<r<1 in S100), andfunction f(3) is employed to calculate an amount of cold state sparkadvance by f(3) (THW, r) (S140).

In FIG. 4, for point A, by f(3) (TH(1), r), wherein r=0.7, an amount ofcold state spark advance is calculated. In this condition engine 10 isoperated, and while temperature THW changes from TH(1) to TH(2) the DIratio also decreases to reach point D. For point D, by f(3) (TH(2), r),wherein r=0.5, an amount of cold state spark advance is calculated. Morespecifically, a timing of ignition is varied by a variation in amount ofspark advance for correction. This indicates that when a DI ratio isneither 0 nor 1 an amount of cold state spark advance is calculated by afunction of the coolant's temperature and DI ratio r, and a variation inamount of spark advance for correction also depends on those of thecoolant in temperature and DI ratio r, respectively.

Thus in a cold state and a transitional period from the cold state to awarm state when an in-cylinder injector and an intake manifold injectorbear shares, respectively, of injecting fuel, not only temperature THWof the coolant of the engine but DI ratio r is also used to calculate anamount of cold state spark advance. If the cylinder's interior and theport are different in temperature and thus have fuel therein atomizeddifferently an accurate spark advance can be provided to combust thefuel satisfactorily.

Furthermore, as will be described hereinafter, three maps may be storedin engine ECU 300 at ROM 320, RAM 340 or the like.

A first map is set as a map applied for DI ratio r=1 (i.e., whenin-cylinder injector 110 alone injects fuel) for a reference timing ofignition, an amount of variation introduced to time ignition, and thelike that time ignition to be maximally retarded. The cylinder receivingfuel injected from in-cylinder injector 110 has high internaltemperature despite a cold state. As such, the injected fuel can beatomized satisfactorily and thus mixed with air to provide asatisfactorily homogeneous air fuel mixture allowing an increasedcombustion rate. As such, if spark retard is introduced a sufficientperiod of time for combustion can still be ensured. Furthermore, ascombustion rate is not a factor significantly limiting a timing ofignition, other factors (e.g., catalyst warm up, exhaust gaspurification, and the like) can be considered in further retarding oradvancing the reference timing of ignition.

A second map is set as a map applied for DI ratio r=0 (i.e., when intakemanifold injector 120 alone injects fuel) for a reference timing ofignition, an amount of variation introduced to time ignition, and thelike that time ignition to be maximally advanced. In a cold state theintake manifold receiving fuel injected from intake manifold injector120 has low temperature. As such, the injected fuel is atomizedunsatisfactorily and thus mixed with air to provide an inhomogeneous airfuel mixture contributing to a decreased combustion rate. Accordingly, afaster timing of ignition must be provided to ensure a sufficient periodof time for combustion.

A third map is set as a map applied for a DI ratio of 0<r<1 (i.e., whenin-cylinder injector 110 and intake manifold injector 120 bear shares,respectively, of injecting fuel) for a reference timing of ignition, anamount of variation introduced to time ignition, and the like that timeignition to be more retarded for higher DI ratio r. As DI ratio rincreases, the fuel is atomized more satisfactorily and thus mixed withair to provide a more satisfactorily homogeneous air fuel mixtureallowing a higher combustion rate. Accordingly, spark retard isintroduced.

Engine ECU 300 prepares three maps for such reference timings ofignition, amounts of variation introduced to time ignition, and thelike, and in accordance with a ratio of in-cylinder injector 110 bearinga share of injecting fuel, or DI ratio r, selects one of the maps toswitch a map of a reference timing of ignition, a map of an amount ofvariation introduced to time ignition, and the like. In accordance withthe selected map engine ECU 300 calculates a reference timing ofignition. In particular, the third map provides a reference timing ofignition, an amount of variation introduced to time ignition, and thelike varied by DI ratio r. Accordingly, not only the map but a functioninterpolating an intermediate portion set in the map may also bepreviously calculated and stored, and used to provide interpolation.

Thus one of the three maps (DI ratio: r=1, r=0, and 0<r<1) can beselected by DI ratio r and used to calculate a reference timing ofignition, an amount of variation introduced to time ignition, and thelike. An appropriate reference timing of ignition corresponding to DIratio r can thus be calculated and set, and detrimental effects ofexcessive spark retard and advance can be prevented.

Engine (1) Suitable for Application of the Control Apparatus

An engine (1) suitable for application of the control apparatus in thepresent embodiment will be described hereinafter.

Referring to FIGS. 5 and 6, maps each indicating a fuel injection ratiobetween in-cylinder injector 10 and intake manifold injector 120,identified as information associated with an operation state of engine10, will now be described. Herein, the fuel injection ratio between thetwo injectors will also be expressed as a ratio of the quantity of thefuel injected from in-cylinder injector 10 to the total quantity of thefuel injected, which is referred to as the “fuel injection ratio ofin-cylinder injector 110”, or, a “DI (Direct Injection) ratio (r)”. Themaps are stored in ROM 320 of engine ECU 300. FIG. 5 shows the map forthe warm state of engine 10, and FIG. 6 shows the map for the cold stateof engine 10.

In the maps shown in FIGS. 5 and 6, with the horizontal axisrepresenting an engine speed of engine 10 and the vertical axisrepresenting a load factor, the fuel injection ratio of in-cylinderinjector 110, or the DI ratio r, is expressed in percentage.

As shown in FIGS. 5 and 6, the DI ratio r is set for each operationregion that is determined by the engine speed and the load factor ofengine 10. “DI RATIO r=100%” represents the region where fuel injectionis carried out using only in-cylinder injector 110, and “DI RATIO r=0%”represents the region where fuel injection is carried out using onlyintake manifold injector 120. “DI RATIO r≠0%”, “DI RATIO≠100%” and“0%<DI RATIO r<100%” each represent the region where fuel injection iscarried out using both in-cylinder injector 110 and intake manifoldinjector 120. Generally, in-cylinder injector 110 contributes to anincrease of output performance, while intake manifold injector 120contributes to uniformity of the air-fuel mixture. These two kinds ofinjectors having different characteristics are appropriately selecteddepending on the engine speed and the load factor of engine 10, so thatonly homogeneous combustion is conducted in the normal operation stateof engine 10 (other than the abnormal operation state such as a catalystwarm-up state during idling, for example).

Further, as shown in FIGS. 5 and 6, the fuel injection ratio betweenin-cylinder injector 110 and intake manifold injector 120 is defined asthe DI ratio r, individually in the maps for the warm state and the coldstate of the engine. The maps are configured to indicate differentcontrol regions of in-cylinder injector 110 and intake manifold injector120 as the temperature of engine 10 changes. When the temperature ofengine 10 detected is equal to or higher than a predeterminedtemperature threshold value, the map for the warm state shown in FIG. 5is selected; otherwise, the map for the cold state shown in FIG. 6 isselected. One or both of in-cylinder injector 110 and intake manifoldinjector 120 are controlled based on the selected map and according tothe engine speed and the load factor of engine 10.

The engine speed and the load factor of engine 10 set in FIGS. 5 and 6will now be described. In FIG. 5, NE(1) is set to 2500 rpm to 2700 rpm,KL(1) is set to 30% to 50%, and KL(2) is set to 60% to 90%. In FIG. 6,NE(3) is set to 2900 rpm to 3100 rpm. That is, NE(1)<NE(3). NE(2) inFIG. 5 as well as KL(3) and KL(4) in FIG. 6 are also set as appropriate.

When comparing FIG. 5 and FIG. 6, NE(3) of the map for the cold stateshown in FIG. 6 is greater than NE(1) of the map for the warm stateshown in FIG. 5. This shows that, as the temperature of engine 10 islower, the control region of intake manifold injector 120 is expanded toinclude the region of higher engine speed. That is, when engine 10 iscold, deposits are unlikely to accumulate in the injection hole ofin-cylinder injector 110 (even if the fuel is not injected fromin-cylinder injector 110). Thus, the region where the fuel injection isto be carried out using intake manifold injector 120 can be expanded, tothereby improve homogeneity.

When comparing FIG. 5 and FIG. 6, “DI RATIO r=100%” holds in the regionwhere the engine speed of engine 10 is equal to or higher than NE(1) inthe map for the warm state, and in the region where the engine speed isNE(3) or higher in the map for the cold state. Further, “DI RATIOr=100%” holds in the region where the load factor is KL(2) or greater inthe map for the warm state, and in the region where the load factor isKL(4) or greater in the map for the cold state. This means that fuelinjection is carried out using only in-cylinder injector 110 in theregion where the engine speed is at a predetermined high level, and thatfuel injection is carried out using only in-cylinder injector 110 in theregion where the engine load is at a predetermined high level, since forthe high speed region and the low load region the engine 10 speed andload are high and a large quantity of air is intaken, and in-cylinderinjector 110 can singly be used to inject fuel to provide a homogeneousair fuel mixture. In this case, the fuel injected from in-cylinderinjector 110 is atomized within the combustion chamber involving latentheat of vaporization (by absorbing heat from the combustion chamber).Accordingly, the temperature of the air-fuel mixture is decreased at thecompression side, and thus, the antiknock performance improves. Further,with the temperature of the combustion chamber decreased, intakeefficiency improves, leading to high power output.

In the map for the warm state in FIG. 5, fuel injection is also carriedout using only in-cylinder injector 110 when the load factor is KL(1) orless. This shows that in-cylinder injector 110 alone is used in apredetermined low load region when the temperature of engine 10 is high.When engine 10 is in the warm state, deposits are likely to accumulatein the injection hole of in-cylinder injector 110. However, when fuelinjection is carried out using in-cylinder injector 110, the temperatureof the injection hole can be lowered, whereby accumulation of depositsis prevented. Further, clogging of in-cylinder injector 110 may beprevented while ensuring a minimum fuel injection quantity thereof.Thus, in-cylinder injector 110 alone is used in the relevant region.

When comparing FIG. 5 and FIG. 6, there is a region of “DI RATIO r=0%”only in the map for the cold state in FIG. 6. This shows that fuelinjection is carried out using only intake manifold injector 120 in apredetermined low load region (KL(3) or less) when the temperature ofengine 10 is low. When engine 10 is cold and low in load and the intakeair quantity is small, atomization of the fuel is unlikely to occur. Insuch a region, it is difficult to ensure favorable combustion with thefuel injection from in-cylinder injector 110. Further, particularly inthe low-load and low-speed region, high power output using in-cylinderinjector 110 is unnecessary. Accordingly, fuel injection is carried outusing intake manifold injector 120 alone, rather than using in-cylinderinjector 110, in the relevant region.

Further, in an operation other than the normal operation, i.e., in thecatalyst warm-up state at idle of engine 10 (abnormal operation state),in-cylinder injector 110 is controlled to carry out stratified chargecombustion. By causing the stratified charge combustion during thecatalyst warm-up operation, warming up of the catalyst is promoted, andexhaust emission is thus improved.

Engine (2) Suitable for Application of the Control Apparatus

An engine (2) suitable for application of the control apparatus in thepresent embodiment will be described hereinafter. In the followingdescription of engine (2) the same description as that of engine (1)will not be repeated.

Referring to FIGS. 7 and 8, maps each indicating a fuel injection ratiobetween in-cylinder injector 110 and intake manifold injector 120,identified as information associated with an operation state of engine10, will now be described. The maps are stored in ROM 320 of engine ECU300. FIG. 7 shows the map for the warm state of engine 10, and FIG. 8shows the map for the cold state of engine 10.

When comparing FIG. 7 and FIG. 8, the figures differ from FIGS. 5 and 6,as follows: “DI RATIO r=100%” holds in the region where the engine speedof engine 10 is equal to or higher than NE(1) in the map for the warmstate, and in the region where the engine speed is NE(3) or higher inthe map for the cold state. Further, except for the low-speed region,“DI RATIO r=100%” holds in the region where the load factor is KL(2) orgreater in the map for the warm state, and in the region where the loadfactor is KL(4) or greater in the map for the cold state. This meansthat fuel injection is carried out using only in-cylinder injector 110in the region where the engine speed is at a predetermined high level,and that fuel injection is often carried out using only in-cylinderinjector 110 in the region where the engine load is at a predeterminedhigh level. However, in the low-speed and high-load region, mixing of anair-fuel mixture formed by the fuel injected from in-cylinder injector110 is poor, and such inhomogeneous air-fuel mixture within thecombustion chamber may lead to unstable combustion. Accordingly, thefuel injection ratio of in-cylinder injector 110 is increased as theengine speed increases where such a problem is unlikely to occur,whereas the fuel injection ratio of in-cylinder injector 110 isdecreased as the engine load increases where such a problem is likely tooccur. These changes in the fuel injection ratio of in-cylinder injector110, or, the DI ratio r, are shown by crisscross arrows in FIGS. 7 and8. In this manner, variation in output torque of the engine attributableto the unstable combustion can be suppressed. It is noted that thesemeasures are approximately equivalent to the measures to decrease thefuel injection ratio of in-cylinder injector 110 as the state of theengine moves toward the predetermined low speed region, or to increasethe fuel injection ratio of in-cylinder injector 110 as the engine statemoves toward the predetermined low load region. Further, except for therelevant region (indicated by the crisscross arrows in FIGS. 7 and 8),in the region where fuel injection is carried out using only in-cylinderinjector 110 (on the high speed side and on the low load side), ahomogeneous air-fuel mixture is readily obtained even when the fuelinjection is carried out using only in-cylinder injector 110. In thiscase, the fuel injected from in-cylinder injector 110 is atomized withinthe combustion chamber involving latent heat of vaporization (byabsorbing heat from the combustion chamber). Accordingly, thetemperature of the air-fuel mixture is decreased at the compressionside, and thus, the antiknock performance improves. Further, with thetemperature of the combustion chamber decreased, intake efficiencyimproves, leading to high power output.

In engine 10 described with reference to FIGS. 5-8, homogeneouscombustion is achieved by setting the fuel injection timing ofin-cylinder injector 110 in the intake stroke, while stratified chargecombustion is achieved by setting it in the compression stroke. That is,when the fuel injection timing of in-cylinder injector 110 is set in thecompression stroke, a rich air-fuel mixture can be located locallyaround the spark plug, so that a lean air-fuel mixture in the combustionchamber as a whole is ignited to realize the stratified chargecombustion. Even if the fuel injection timing of in-cylinder injector110 is set in the intake stroke, stratified charge combustion can berealized if it is possible to locate a rich air-fuel mixture locallyaround the spark plug.

As used herein, the stratified charge combustion includes both thestratified charge combustion and semi-stratified charge combustion. Inthe semi-stratified charge combustion, intake manifold injector 120injects fuel in the intake stroke to generate a lean and homogeneousair-fuel mixture in the whole combustion chamber, and then in-cylinderinjector 110 injects fuel in the compression stroke to generate a richair-fuel mixture around the spark plug, so as to improve the combustionstate. Such semi-stratified charge combustion is preferable in thecatalyst warm-up operation for the following reasons. In the catalystwarm-up operation, it is necessary to considerably retard the ignitiontiming and maintain favorable combustion state (idling state) so as tocause a high-temperature combustion gas to reach the catalyst. Further,a certain quantity of fuel needs to be supplied. If the stratifiedcharge combustion is employed to satisfy these requirements, thequantity of the fuel will be insufficient. With the homogeneouscombustion, the retarded amount for the purpose of maintaining favorablecombustion is small compared to the case of stratified chargecombustion. For these reasons, the above-described semi-stratifiedcharge combustion is preferably employed in the catalyst warm-upoperation, although either of stratified charge combustion andsemi-stratified charge combustion may be employed.

Furthermore in the engine described with reference to FIGS. 5-8preferably in-cylinder injector 110 is timed to inject fuel at thecompression stroke for the following reason, although in engine 10described above, the fuel injection timing of in-cylinder injector 110is set in the intake stroke in a basic region corresponding to thealmost entire region (herein, the basic region refers to the regionother than the region where semi-stratified charge combustion isconducted by causing intake manifold injector 120 to inject the fuel inthe intake stroke and causing in-cylinder injector 110 to inject thefuel in the compression stroke, which is conducted only in the catalystwarm-up state). The fuel injection timing of in-cylinder injector 110,however, may be set temporarily in the compression stroke for thepurpose of stabilizing combustion, for the following reasons.

When the fuel injection timing of in-cylinder injector 110 is set in thecompression stroke, the air-fuel mixture is cooled by the injected fuelwhile the temperature in the cylinder is relatively high. This improvesthe cooling effect and, hence, the antiknock performance. Further, whenthe fuel injection timing of in-cylinder injector 110 is set in thecompression stroke, the time from the fuel injection to the ignition isshort, which ensures strong penetration of the injected fuel, so thatthe combustion rate increases. The improvement in antiknock performanceand the increase in combustion rate can prevent variation in combustion,and thus, combustion stability is improved.

Note that in the above described flowchart at S150 whenever theflowchart is executed a reference timing of ignition may be calculatedfrom the engine 10 operation state and function g correcting thereference timing of ignition by an amount of cold state spark advancemay be used to calculate a timing of ignition.

Furthermore, irrespectively of the engine 10 temperature (i.e., ineither a warm state or a cold state) when idling is off (i.e., an idleswitch is off, the accelerator pedal is pressed) the FIG. 5 or 7 map fora warm state may be used. (Regardless of cold or warm state, in-cylinderinjector 110 is used for a low load range.)

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. A control apparatus for an internal combustion engine having a firstfuel injection mechanism injecting fuel into a cylinder and a secondfuel injection mechanism injecting the fuel into an intake manifold,comprising: a controller controlling said first and second fuelinjection mechanisms to bear shares, respectively, of injecting the fuelat a ratio calculated as based on a condition required for said internalcombustion engine; a detector detecting a temperature of said internalcombustion engine; and an ignition timing controller controlling anignition device to vary a timing of ignition, wherein said ignitiontiming controller uses said ratio and said temperature to calculate anamount of variation introduced to time said internal combustion engineto be ignited in a cold state and applies said amount to control saidignition device to vary said timing of ignition.
 2. A control apparatusfor an internal combustion engine having a first fuel injectionmechanism injecting fuel into a cylinder and a second fuel injectionmechanism injecting the fuel into an intake manifold, comprising: acontroller controlling said first and second fuel injection mechanismsto bear shares, respectively, of injecting the fuel at a ratiocalculated as based on a condition required for said internal combustionengine; a detector detecting a temperature of said internal combustionengine; a calculator calculating a reference timing of ignition; and anignition timing controller using an amount of variation introduced totime ignition to control an ignition device to vary said referencetiming of ignition, wherein said ignition timing controller uses saidratio and said temperature to calculate an amount of variationintroduced to time said internal combustion engine to be ignited in acold state and applies said amount to control said ignition device tovary said reference timing of ignition.
 3. A control apparatus for aninternal combustion engine having a first fuel injection mechanisminjecting fuel into a cylinder and a second fuel injection mechanisminjecting the fuel into an intake manifold, comprising: a controllercontrolling said first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for said internal combustion engine; adetector detecting a temperature of said internal combustion engine; andan ignition timing controller controlling an ignition device to vary atiming of ignition, wherein said ignition timing controller uses saidratio and said temperature to calculate an amount of spark advance ofsaid internal combustion engine in a cold state and applies said amountto control said ignition device to vary said timing of ignition.
 4. Acontrol apparatus for an internal combustion engine having a first fuelinjection mechanism injecting fuel into a cylinder and a second fuelinjection mechanism injecting the fuel into an intake manifold,comprising: a controller controlling said first and second fuelinjection mechanisms to bear shares, respectively, of injecting the fuelat a ratio calculated as based on a condition required for said internalcombustion engine; a detector detecting a temperature of said internalcombustion engine; a calculator calculating a reference timing ofignition; and an ignition timing controller using an amount of sparkadvance for correction to control an ignition device to vary saidreference timing of ignition, wherein said ignition timing controlleruses said ratio and said temperature to calculate an amount of sparkadvance of said internal combustion engine for correction in a coldstate and applies said amount to control said ignition device to varysaid reference timing of ignition.
 5. The control apparatus according toclaim 3, wherein said ignition timing controller calculates said amountof spark advance to be decreased when said first fuel injectionmechanism is increased in said ratio.
 6. The control apparatus accordingto claim 3, wherein said ignition timing controller calculates saidamount of spark advance to be increased when said second fuel injectionmechanism is increased in said ratio.
 7. The control apparatus accordingto claim 3, wherein said ignition timing controller calculates saidamount of spark advance to be decreased when said temperature isincreased.
 8. The control apparatus according to claim 3, wherein saidignition timing controller calculates said amount of spark advance to beincreased when said temperature is decreased.
 9. A control apparatus foran internal combustion engine having a first fuel injection mechanisminjecting fuel into a cylinder and a second fuel injection mechanisminjecting the fuel into an intake manifold, comprising: a controllercontrolling said first and second fuel injection mechanisms to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for said internal combustion engine, saidratio including preventing one of said fuel injection mechanisms frominjecting the fuel; a detector detecting a temperature of said internalcombustion engine; a storage storing a reference timing of ignition andan amount of variation introduced to time ignition in a cold state; andan ignition timing controller controlling an ignition device by varyingsaid reference timing of ignition by said amount to provide a variedtiming of ignition, wherein said storage stores said amount of variationintroduced to time said internal combustion engine to be ignited in saidcold state, said amount being calculated as based on a condition of amixture of the fuel injected through said fuel injection mechanism andair.
 10. The control apparatus according to claim 9, wherein saidstorage stores said amount calculated from said temperature and saidratio.
 11. The control apparatus according to claim 10, wherein saidstorage stores said amount in a map.
 12. The control apparatus accordingto claim 11, wherein said storage stores said amount divided into afirst map applied when said first fuel injection mechanism alone injectsthe fuel, a second map applied when said second fuel injection mechanismalone injects the fuel, and a third map applied when said first andsecond fuel injection mechanisms inject the fuel.
 13. The controlapparatus according to claim 12, wherein said first map provides saidamount set to provide spark retard.
 14. The control apparatus accordingto claim 12, wherein said first map provides said amount set to providespark advance.
 15. The control apparatus according to claim 12, whereinsaid third map provides said amount set to provide spark retard whensaid first fuel injection mechanism is increased in said ratio.
 16. Thecontrol apparatus according to claim 12, wherein said third map providessaid amount set to provide spark advance when said second fuel injectionmechanism is increased in said ratio.
 17. The control apparatusaccording to claim 1, wherein said first fuel injection mechanism is anin-cylinder injector and said second fuel injection mechanism is anintake manifold injector.
 18. A control apparatus for an internalcombustion engine having first fuel injection means for injecting fuelinto a cylinder and second fuel injection means for injecting the fuelinto an intake manifold, comprising: control means for controlling saidfirst and second fuel injection means to bear shares, respectively, ofinjecting the fuel at a ratio calculated as based on a conditionrequired for said internal combustion engine; detection means fordetecting a temperature of said internal combustion engine; and ignitiontiming control means for controlling an ignition device to vary a timingof ignition, wherein said ignition timing control means includes meansusing said ratio and said temperature to calculate an amount ofvariation introduced to time said internal combustion engine to beignited in a cold state and apply said amount for controlling saidignition device to vary said timing of ignition.
 19. A control apparatusfor an internal combustion engine having first fuel injection means forinjecting fuel into a cylinder and second fuel injection means forinjecting the fuel into an intake manifold, comprising: control meansfor controlling said first and second fuel injection means to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for said internal combustion engine;detection means for detecting a temperature of said internal combustionengine; calculation means for calculating a reference timing ofignition; and ignition timing control means using an amount of variationintroduced to time ignition for controlling an ignition device to varysaid reference timing of ignition, wherein said ignition timing controlmeans includes means using said ratio and said temperature to calculatean amount of variation introduced to time said internal combustionengine to be ignited in a cold state and apply said amount forcontrolling said ignition device to vary said reference timing ofignition.
 20. A control apparatus for an internal combustion enginehaving first fuel injection means for injecting fuel into a cylinder andsecond fuel injection means for injecting the fuel into an intakemanifold, comprising: a control means for controlling said first andsecond fuel injection means to bear shares, respectively, of injectingthe fuel at a ratio calculated as based on a condition required for saidinternal combustion engine; detection means for detecting a temperatureof said internal combustion engine; and ignition timing control meansfor controlling an ignition device to vary a timing of ignition, whereinsaid ignition timing control means includes means using said ratio andsaid temperature to calculate an amount of spark advance of saidinternal combustion engine in a cold state and apply said amount forcontrolling said ignition device to vary said timing of ignition.
 21. Acontrol apparatus for an internal combustion engine having first fuelinjection means for injecting fuel into a cylinder and second fuelinjection means for injecting the fuel into an intake manifold,comprising: control means for controlling said first and second fuelinjection means to bear shares, respectively, of injecting the fuel at aratio calculated as based on a condition required for said internalcombustion engine; detection means for detecting a temperature of saidinternal combustion engine; calculation means for calculating areference timing of ignition; and ignition timing control means using anamount of spark advance for correction for controlling an ignitiondevice to vary said reference timing of ignition, wherein said ignitiontiming control means includes means using said ratio and saidtemperature to calculate an amount of spark advance of said internalcombustion engine for correction in a cold state and apply said amountfor controlling said ignition device to vary said reference timing ofignition.
 22. The control apparatus according to claim 20, wherein saidignition timing control means includes means for calculating said amountof spark advance to be decreased when said first fuel injection means isincreased in said ratio.
 23. The control apparatus according to claim20, wherein said ignition timing control means includes means forcalculating said amount of spark advance to be increased when saidsecond fuel injection means is increased in said ratio.
 24. The controlapparatus according to claim 20, wherein said ignition timing controlmeans includes means for calculating said amount of spark advance to bedecreased when said temperature is increased.
 25. The control apparatusaccording to claim 20, wherein said ignition timing control meansincludes means for calculating said amount of spark advance to beincreased when said temperature is decreased.
 26. A control apparatusfor an internal combustion engine having first fuel injection means forinjecting fuel into a cylinder and second fuel injection means forinjecting the fuel into an intake manifold, comprising: control meansfor controlling said first and second fuel injection means to bearshares, respectively, of injecting the fuel at a ratio calculated asbased on a condition required for said internal combustion engine, saidratio including preventing one of said fuel injection means frominjecting the fuel; detection means for detecting a temperature of saidinternal combustion engine; storage means for storing a reference timingof ignition and an amount of variation introduced to time ignition in acold state; and ignition timing control means for controlling anignition device by varying said reference timing of ignition by saidamount to provide a varied timing of ignition, wherein said storagemeans includes means for storing said amount of variation introduced totime said internal combustion engine to be ignited in said cold state,said amount being calculated as based on a condition of a mixture of thefuel injected through said fuel injection means and air.
 27. The controlapparatus according to claim 26, wherein said storage means includesmeans for storing said amount calculated from said temperature and saidratio.
 28. The control apparatus according to claim 27, wherein saidstorage means includes means for storing said amount in a map.
 29. Thecontrol apparatus according to claim 28, wherein said storage meansincludes means for storing said amount divided into a first map appliedwhen said first fuel injection means alone injects the fuel, a secondmap applied when said second fuel injection means alone injects thefuel, and a third map applied when said first and second fuel injectionmeans inject the fuel.
 30. The control apparatus according to claim 29,wherein said first map provides said amount set to provide spark retard.31. The control apparatus according to claim 29, wherein said first mapprovides said amount set to provide spark advance.
 32. The controlapparatus according to claim 29, wherein said third map provides saidamount set to provide spark retard when said first fuel injection meansis increased in said ratio.
 33. The control apparatus according to claim29, wherein said third map provides said amount set to provide sparkadvance when said second fuel injection means is increased in saidratio.
 34. The control apparatus according to claim 18, wherein saidfirst fuel injection means is an in-cylinder injector and said secondfuel injection means is an intake manifold injector.